Storing a secret key for use in encryption or authentication is an important matter. In modern encryption, preventing secret key leaks is a prerequisite to security. Tamper-resistant hardware for storing keys has been studied to prevent secret keys from leaking, and products such as a trusted platform module (TPM) and a hardware security module (HSM) have been put to practical use.
Another method of preventing secret information from being divulged because of leakage of a secret key is to update the secret key. That type of technique has already been known, as disclosed in Patent literature 1.